Semiconductor device, solid-state imaging device, and imaging device

ABSTRACT

A semiconductor device includes a first substrate, a second substrate, a connection part, and an alignment mark. The connection part includes a first electrode which is disposed on the first substrate, a second electrode which is disposed on the second substrate, and a connection bump which connects the first electrode and the second electrode. The alignment mark includes a first mark which is disposed on the first substrate and a second mark which is disposed on the second substrate. A sum of a height of the first mark and a height of the second mark is substantially equal to a sum of a height of the first electrode, a height of the second electrode, and a height of the connection bump.

This application is a continuation application based on PCT PatentApplication No. PCT/JP2014/059547, filed Mar. 31, 2014, whose priorityis claimed on Japanese Patent Application No. 2013-121045, filed Jun. 7,2013. The contents of both the PCT Patent Application and the JapanesePatent Application are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a semiconductor device, a solid-stateimaging device, and an imaging device which are formed by connecting aplurality of substrates with each other.

Description of Related Art

In recent years, video cameras, electronic still cameras, and the likehave been widely circulated among the public. In such cameras,charge-coupled device (CCD)-type or amplification-type solid-stateimaging devices are used. In such an amplification-type solid-stateimaging device, signal charges generated by and accumulated inphotoelectric conversion units of pixels which receive incident lightare guided to amplification units provided in the pixels. Signalsamplified by the amplification units are output from the pixels. In anamplification-type solid-state imaging device, a plurality of suchpixels are arrayed in a two-dimensional matrix shape. Amplification-typesolid-state imaging devices include, for example, complementary metaloxide semiconductor (CMOS)-type solid-state imaging devices which useCMOS transistors, and the like.

In the related art, a general CMOS-type solid-state imaging deviceemploys a scheme in which signal charges generated by photoelectricconversion units of each of pixels arrayed in a two-dimensional matrixshape are sequentially read out for each row. In this scheme, since atiming of light exposure in the photoelectric conversion units of thepixels is decided based on a start and an end of readout of the signalcharge, timings of light exposure are different in rows. For thisreason, when a fast-moving subject is imaged using such a CMOS-typesolid-state imaging device, the subject becomes distorted in a capturedimage.

In order to remove distortion of a subject, a simultaneous imagingfunction (global shutter function) which realizes simultaneity inaccumulation of signal charges has been proposed. In addition,applications of CMOS-type solid-state imaging devices with the globalshutter function are becoming diverse. A CMOS-type solid-state imagingdevice with the global shutter function generally needs to have anaccumulation capacitor which has a light-shielding property toaccumulate signal charges generated by photoelectric conversion unitsbefore the signal charges are read out. In such a CMOS-type solid-stateimaging device of the related art, after all pixels are simultaneouslyexposed, signal charges generated by photoelectric conversion units aresimultaneously transferred to accumulation capacitors in all of thepixels and temporarily accumulated for the moment. The accumulatedsignal charges are sequentially converted into pixel signals and readout at predetermined readout timings.

In a CMOS-type solid-state imaging device with the global shutterfunction of the related art, photoelectric conversion units andaccumulation capacitors need to be created on the same plane of the samesubstrate, and thus the size of the substrate increases. Furthermore,during a waiting period before signal charges accumulated in theaccumulation capacitors are read out, quality of signals deterioratesdue to noise caused by light or noise caused by a leaking current (darkcurrent) occurring in the accumulation capacitors.

Japanese Unexamined Patent Application, First Publication No. 2006-49361discloses a solid-state imaging device to solve the above problems. Thissolid-state imaging device includes a MOS image sensor substrate onwhich micropads are formed on a wiring layer side for each unit cell anda signal-processing substrate on which micropads are formed on thewiring layer side at the position corresponding to the micropads of theMOS image sensor substrate. The MOS image sensor substrate and thesignal-processing substrate are connected to each other by microbumps.In addition, Japanese Unexamined Patent Application, First PublicationNo. 2010-219339 discloses a method for preventing the area of asubstrate from increasing. In this method, a solid-state imaging device,in which a first substrate on which a photoelectric conversion unit isformed and a second substrate on which a plurality of MOS transistorsare formed are bonded, is used.

In a process in which two substrates (for example, the MOS image sensorsubstrate and the signal-processing substrate) constituting asemiconductor device such as a solid-state imaging device are connectedusing microbumps (which will be described hereinafter as bumps) or thelike, there is a process of performing positioning of substrates(alignment) in order to prevent deviation during connection (alignmentprocess). Each substrate has a mark that is called an alignment mark.For example, there is an alignment mark obtained by using a baseelectrode for forming a bump which connects substrates.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a semiconductordevice includes: a first substrate; a second substrate; a connectionpart which electrically connects the first substrate and the secondsubstrate; and an alignment mark which is used in alignment of the firstsubstrate and the second substrate. The connection part includes: afirst electrode which is disposed on the first substrate; a secondelectrode which is disposed on the second substrate; and a connectionbump which is disposed between the first electrode and the secondelectrode and which electrically connects the first electrode and thesecond electrode. The alignment mark includes: a first mark which isdisposed on the first substrate; and a second mark which is disposed onthe second substrate at a position which corresponds to the position ofthe first mark and which is insulated from the first mark. A sum of aheight of the first mark and a height of the second mark issubstantially equal to a sum of a height of the first electrode, aheight of the second electrode, and a height of the connection bump.

According to a second aspect of the present invention, in thesemiconductor device according to the first aspect of the presentinvention, the height of the second mark may be substantially equal to asum of the height of the second electrode and the height of theconnection bump.

According to a third aspect of the present invention, in thesemiconductor device according to the second aspect of the presentinvention, the first mark may be an electrode which is disposed on thefirst substrate. The second mark may be a bump which is disposed on thesecond substrate.

According to a fourth aspect of the present invention, in thesemiconductor device according to the third aspect of the presentinvention, when the first substrate and the second substrate are seen inplan view, the first mark may surround the second mark.

According to a fifth aspect of the present invention, in thesemiconductor device according to the third aspect of the presentinvention, the bump may be connected with the second substrate and asurface of a base electrode which is formed on a surface of the secondsubstrate. A width of the base electrode may be equal to or smaller thana width of the bump.

According to a sixth aspect of the present invention, a solid-stateimaging device includes the semiconductor device according to any one ofthe first to fifth aspects of the present invention. The first substrateincludes a photoelectric conversion element which is configured tooutput a signal depending on an amount of incident light. The secondsubstrate includes a processing circuit which is configured to processthe signal output from the photoelectric conversion element.

According to a seventh aspect of the present invention, a solid-stateimaging device includes the semiconductor device according to any one ofthe third to fifth aspects of the present invention. The secondsubstrate includes a photoelectric conversion element which isconfigured to output a signal depending on an amount of incident light.The first substrate includes a processing circuit which is configured toprocess the signal output from the photoelectric conversion element.

According to an eighth aspect of the present invention, an imagingdevice includes the solid-state imaging device according to the sixth orseventh aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes a plan view and a cross-sectional view showing aconfiguration of a main part of a semiconductor device according to anembodiment of the present invention.

FIG. 2A is a cross-sectional view showing a manufacturing process of aconnection part and an alignment mark of the semiconductor deviceaccording to the embodiment of the present invention.

FIG. 2B is a cross-sectional view showing the manufacturing process ofthe connection part and the alignment mark of the semiconductor deviceaccording to the embodiment of the present invention.

FIG. 2C is a cross-sectional view showing the manufacturing process ofthe connection part and the alignment mark of the semiconductor deviceaccording to the embodiment of the present invention.

FIG. 2D is a cross-sectional view showing the manufacturing process ofthe connection part and the alignment mark of the semiconductor deviceaccording to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of the semiconductor device in analignment process of the semiconductor device according to theembodiment of the present invention.

FIG. 4 is a plan view of a semiconductor substrate which constitutes thesemiconductor device according to the embodiment of the presentinvention.

FIG. 5 is a block diagram showing a configuration of an imaging deviceaccording to the embodiment of the present invention.

FIG. 6 is a plan view and a cross-sectional view showing anotherconfiguration of the main part of the semiconductor device according tothe embodiment of the present invention.

FIG. 7 is a plan view and a cross-sectional view showing still anotherconfiguration of the main part of the semiconductor device according tothe embodiment of the present invention.

FIG. 8 shows a plan view and a cross-sectional view showing stillanother configuration of the main part of the semiconductor deviceaccording to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. An example of a semiconductor device whichhas two substrates, a connection part which electrically connects thesesubstrates, and an alignment mark to be used in alignment of thesesubstrates will be described below. The semiconductor device accordingto the present embodiment is a device which can exchange signals betweenthe two substrates via the connection part. The semiconductor deviceaccording to the present embodiment is, for example, a solid-stateimaging device which has a photoelectric conversion element and performsimaging of subjects.

FIG. 1 shows a configuration of a main part of the semiconductor deviceaccording to the present embodiment. The upper drawing of FIG. 1 shows astate of an alignment mark provided in the semiconductor device seen inplan view. The lower drawing of FIG. 1 shows a cross-section of thesemiconductor device. The configuration shown in FIG. 1 will bedescribed below.

A semiconductor device 3 according to the present embodiment has asemiconductor substrate (a first substrate, a second substrate) 1,another semiconductor substrate (a first substrate, a second substrate)2, a connection part 10, and an alignment mark 20. The semiconductorsubstrate 1 and the semiconductor substrate 2 are formed of a materialincluding a semiconductor such as silicon. A main surface (a surfacewith a larger surface area than a side surface) of the semiconductorsubstrate 1 and a main surface of the semiconductor substrate 2 faceeach other. The semiconductor substrate 1 and the semiconductorsubstrate 2 are connected to each other by the connection part 10. Whenthe semiconductor device 3 is a solid-state imaging device, thesemiconductor substrate 1 corresponds to, for example, the firstsubstrate on which a photoelectric conversion unit is formed. Thesemiconductor substrate 2 corresponds to, for example, the secondsubstrate on which a plurality of MOS transistors are formed. In therespective semiconductor substrate 1 and the semiconductor substrate 2,wiring layers which electrically connect circuits disposed on thesubstrates are formed in a plurality of layers. The wiring layers ondifferent layers are connected to each other via through-holes or vias.FIG. 1 only illustrates a portion around the surfaces of thesemiconductor substrate 1 and the semiconductor substrate 2, andremaining portions are not illustrated (the same applies to FIGS. 3, and6 to 8).

The connection part 10 has a base electrode (a first electrode, a secondelectrode) 11, another base electrode (a first electrode, a secondelectrode) 12, and a bump (connection bump) 13. The base electrode 11 isformed on the surface of the semiconductor substrate 1. The baseelectrode 12 is formed on the surface of the semiconductor substrate 2.The bump 13 connects the base electrode 11 and the base electrode 12.The base electrode 11, the base electrode 12, and the bump 13 are formedof a conductive material, for example, a metal. The base electrode 11and the base electrode 12 are formed as, for example, a thin film. Thebump 13 is formed as, for example, a columnar structure. The uppersurface of the bump 13 is connected with a surface of the base electrode11. The lower surface of the bump 13 is connected with a surface of thebase electrode 12. After the bump 13 is formed on the surface of thebase electrode 12, the bump 13 is connected with the base electrode 11when the semiconductor substrate 1 and the semiconductor substrate 2 areconnected to each other.

The base electrode 11 is connected with a through-hole 31 formed insidethe semiconductor substrate 1. The through-hole 31 is exposed on thesurface of the semiconductor substrate 1. The exposed portion of thethrough-hole 31 is connected with the base electrode 11. Thethrough-hole 31 is connected to a wiring layer formed inside thesemiconductor substrate 1, which is not illustrated. The base electrode12 is connected with another through-hole 32 formed inside thesemiconductor substrate 2. The through-hole 32 is exposed on the surfaceof the semiconductor substrate 2. The exposed portion of thethrough-hole 32 is connected with the base electrode 12. Thethrough-hole 32 is connected to a wiring layer formed inside thesemiconductor substrate 2, which is not illustrated. With theabove-described structure, the semiconductor substrate 1 and thesemiconductor substrate 2 are electrically connected. For this reason,signals can be transmitted between the semiconductor substrate 1 and thesemiconductor substrate 2 via the connection part 10.

The alignment mark 20 has a base electrode (a first mark) 21, anotherbase electrode 22, and a bump (a second mark) 23. The base electrode 21is formed on the surface of the semiconductor substrate 1. The baseelectrode 22 is formed on the surface of the semiconductor substrate 2.The bump 23 is formed on the surface of the semiconductor substrate 2.The base electrode 21, the base electrode 22, and the bump 23 are formedof a conductive material, for example, a metal. The base electrode 21and the base electrode 22 are formed as, for example, a thin film. Thebase electrode 22 is an electrode to which, when the bump 23 is formedthrough electroless plating to be described below, the plating formingthe bump 23 is attached. The bump 23 is formed as, for example, acolumnar structure. The bump 23 is connected with a surface of the baseelectrode 22. The bump 23 entirely covers the surface of the baseelectrode 22. A part of the bump 23 is connected with the surface of thesemiconductor substrate 2. In the state in which the semiconductorsubstrate 1 is connected to the semiconductor substrate 2, the bump 23is not connected with the semiconductor substrate 1. In this state,there is a space between a surface of the bump 23 and the surface of thesemiconductor substrate 1.

When the semiconductor substrate 1 and the semiconductor substrate 2 areseen in plan view, the base electrode 21 has an annular shape (a hollowcircle), and the base electrode 22 and the bump 23 have circular shapes.When the semiconductor substrate 1 and the semiconductor substrate 2 areseen in plan view, the base electrode 21 is formed to surround theperimeter of the base electrode 22 and the bump 23. When thesemiconductor substrate 1 and the semiconductor substrate 2 are seen inplan view, the diameter of the bump 23 is larger than the diameter ofthe base electrode 22, and the area of the bump 23 is greater than thearea of the base electrode 22. When the semiconductor substrate 1 andthe semiconductor substrate 2 are seen in plan view, the width of thebase electrode 22 (the width in the direction parallel with the surfaceof the semiconductor substrate 2; for example, the diameter) ispreferably equal to or smaller than the width of the bump 23.

When the semiconductor substrate 1 and the semiconductor substrate 2 areseen in plan view, the base electrode 22 is disposed at a position onthe semiconductor substrate 2 which corresponds to the position of thebase electrode 21 of the semiconductor substrate 1. That is, whenrespective positions of the semiconductor substrate 1 and thesemiconductor substrate 2 are adjusted so that the base electrode 11 andthe bump 13 are connected with each other, the base electrode 22 isdisposed so that the base electrode 22 is positioned further inside thanthe inner circumference of the base electrode 21. To be more specific,when the respective positions of the semiconductor substrate 1 and thesemiconductor substrate 2 are adjusted so that the base electrode 11 andthe bump 13 are connected with each other, the base electrode 22 isdisposed so that the center of the base electrode 22 coincides with thecenter of the base electrode 21. When ideal alignment has beenperformed, the center of the base electrode 21, the center of the baseelectrode 22, and the center of the bump 23 substantially coincide inthe state in which the semiconductor substrate 1 and the semiconductorsubstrate 2 are connected.

The base electrode 21 is formed of the same material that forms the baseelectrode 11. The base electrode 21 is simultaneously formed with thebase electrode 11 in the process of forming the base electrode 11. Thebase electrode 22 is formed of the same material that forms the baseelectrode 12. The base electrode 22 is simultaneously formed with thebase electrode 12 in the process of forming the base electrode 12. Thebump 23 is formed of the same material that forms the bump 13. The bump23 is simultaneously formed with the bump 13 in the process of formingthe bump 13. The base electrode 22 is connected with the through-hole 33which is formed inside the semiconductor substrate 2. The through-hole33 is exposed on the surface of the semiconductor substrate 2. Theexposed portion of the through-hole 33 is connected with the baseelectrode 22. The through-hole 33 is connected to a wiring layer formedinside the semiconductor substrate 2, which is not illustrated.

In an alignment process, IR light (infrared light) is radiated from arear side of the main surface of the semiconductor substrate 2 that isconnected to the semiconductor substrate 1. In this state, the alignmentmark 20 is observed with an IR microscope (infrared microscope) or an IRcamera (infrared camera) from a rear side of the main surface of thesemiconductor substrate 1 that is connected to the semiconductorsubstrate 2. In the alignment process, the relative positions of thesemiconductor substrate 1 and the semiconductor substrate 2 in thehorizontal direction are adjusted so that the size of the gap betweenthe base electrode 21 and the bump 23 is kept uniform within thealignment mark 20 as a whole (in other words, the distance between thebase electrode 21 and the bump 23 is uniform within the alignment mark20 as a whole). In FIG. 1, the distance between the inner circumferenceof the base electrode 21 and the outer circumference of the bump 23 is auniform distance L at any position. By performing alignment so that thedistance between the inner circumference of the base electrode 21 andthe outer circumference of the bump 23 is uniform through the baseelectrode 21 and the bump 23, accuracy in the alignment furtherincreases.

In the semiconductor device 3 shown in FIG. 1, the semiconductorsubstrate 1 corresponds to a first substrate. The semiconductorsubstrate 2 corresponds to a second substrate. The base electrode 11corresponds to a first electrode disposed on the first substrate. Thebase electrode 12 corresponds to a second electrode disposed on thesecond substrate. The base electrode 21 corresponds to a first markdisposed on the first substrate. The bump 23 corresponds to a secondmark disposed at the position on the second substrate corresponding tothe position of the first mark.

In the present embodiment, the sum of the height of the base electrode21 (the width of the base electrode 21 in the vertical direction in thecross-sectional view of FIG. 1; the thickness thereof) and the height ofthe bump 23 (the width of the bump 23 in the vertical direction in thecross-sectional view of FIG. 1; the thickness thereof) is substantiallyequal to the sum of the height of the base electrode 11 (the width ofthe base electrode 11 in the vertical direction in the cross-sectionalview of FIG. 1; the thickness thereof), the height of the base electrode12 (the width of the base electrode 12 in the vertical direction in thecross-sectional view of FIG. 1; the thickness thereof), and the heightof the bump 13 (the width of the bump 13 in the vertical direction inthe cross-sectional view of FIG. 1; the thickness thereof).

In the semiconductor device 3 configured as described above, theposition of the surface of the base electrode 21 and the position of thesurface of the bump 23 are substantially the same in the directionperpendicular to the main surface of the semiconductor substrate 1 orthe semiconductor substrate 2. Thus, these positions (positions on thedashed line D1 of FIG. 1) can be focused. When these positions arefocused, the contour of the base electrode 21 and the contour of thebump 23 can be visually recognized with clarity, and thus accuracy inalignment is improved.

In the present embodiment, the base electrode 11 is simultaneouslyformed with the base electrode 21. The position of the surface of thebase electrode 11 and the position of the surface of the base electrode21 are substantially the same in the direction perpendicular to the mainsurface of the semiconductor substrate 1 or the semiconductor substrate2. In other words, the height of the base electrode 11 is substantiallyequal to the height of the base electrode 21. In the present embodiment,the bump 13 is simultaneously formed with the bump 23. The position of asurface of the bump 13 and the position of a surface of the bump 23 aresubstantially the same in the direction perpendicular to the mainsurface of the semiconductor substrate 1 or the semiconductor substrate2. That is, the height of the bump 23 is substantially equal to the sumof the height of the base electrode 12 and the height of the bump 13. Asa result, when the bump 13 is connected with the base electrode 11, theposition of the surface of the base electrode 21 and the position of thesurface of the bump 23 are substantially the same in the directionperpendicular to the main surface of the semiconductor substrate 1 orthe semiconductor substrate 2. The above-described structure can beeasily formed by simultaneously forming the connection part 10 and thealignment mark 20 with no special control.

In the present embodiment, when the semiconductor substrate 1 and thesemiconductor substrate 2 are seen in plan view, the bump 23 is largerthan the base electrode 22. For this reason, alignment is performed in astate in which the entire base electrode 22 is disposed further insidefrom the outer circumference of the bump 23. In this state, the IR lightradiated from the rear side of the main surface of the semiconductorsubstrate 2 that is connected to the semiconductor substrate 1 isobstructed by the entire outer circumference of the bump 23. Thus,alignment can be performed with reference to the distance between theinner circumference of the base electrode 21 and the outer circumferenceof the bump 23. The position of the surface of the base electrode 21 andthe position of the surface of the bump 23 are substantially the same inthe direction perpendicular to the main surface of the semiconductorsubstrate 1 or the semiconductor substrate 2. For this reason, alignmentcan be successfully performed while focus is on the positions.

On the other hand, when the bump 23 is smaller than the base electrode22, alignment is performed in a state in which the entire bump 23 isdisposed further inside than the outer circumference of the baseelectrode 22. In this state, the IR light radiated from the rear side ofthe main surface of the semiconductor substrate 2 that is connected tothe semiconductor substrate 1 is obstructed by the outer circumferenceof the base electrode 22. Thus, alignment can be performed withreference to the distance between the inner circumference of the baseelectrode 21 and the outer circumference of the base electrode 22. Theposition of the surface of the base electrode 21, however, is differentfrom the position of the surface of the base electrode 22 in thedirection perpendicular to the main surface of the semiconductorsubstrate 1 or the semiconductor substrate 2. For this reason, at leastone of the base electrode 21 and the bump 23 cannot be focused. As aresult, accuracy in alignment easily deteriorates.

As described above, in the present embodiment, the bump 23 is largerthan the base electrode 22. Accordingly, alignment can be performed withreference to the distance between the inner circumference of the baseelectrode 21 and the outer circumference of the bump 23 in a state inwhich the surface of the base electrode 21 and the surface of the bump23 are focused. Therefore, accuracy in the alignment is improved.

FIGS. 2A to 2D show a manufacturing process of the connection part 10and the alignment mark 20. In FIGS. 2A to 2D, a cross-section of thesemiconductor substrate 2 is shown. FIG. 2A shows a state in which,after the base electrodes 12 and the base electrode 22 are formed on thesurface of the semiconductor substrate 2, a thin film of a resist 34 isformed on the surface of the semiconductor substrate 2. The resist 34 isformed such that the height of the resist 34 is higher than the heightsof the base electrodes 12 and the base electrode 22. In other words, allsurfaces of the base electrodes 12 and the base electrode 22 (excludingthe surfaces connected with the semiconductor substrate 2) are coveredby the resist 34. When the semiconductor substrate 2 is seen in planview, the base electrodes 12 and the base electrode 22 are formed suchthat the width of the base electrode 22 is smaller than the width ofeach base electrode 12. When the semiconductor substrate 2 is seen inplan view, the base electrode 22 is formed in a circular shape.

FIG. 2B shows a state in which the resist 34 at positions at which thebumps 13 and the bump 23 are to be formed is patterned. Opening partsare formed at the positions at which the base electrodes 12 are formedby removing the resist 34 through etching so that parts of the surfacesof the base electrodes 12 are exposed. Corners of the surfaces of thebase electrodes 12 are covered by the resist 34. An opening part isformed at the position at which the base electrode 22 is formed byremoving the resist 34 through etching so that the entire surface of thebase electrode 22 (excluding the surface connected with thesemiconductor substrate 2) and the surface of the semiconductorsubstrate 2 around the base electrode 22 are exposed. When thesemiconductor substrate 2 is seen in plan view, the shape of the openingpart formed corresponding to the base electrodes 12 coincides with theshape of the bump 13. The shape of the opening part formed correspondingto the base electrodes 22 coincides with the shape of the bump 23.

FIG. 2C shows a state in which the bumps 13 and the bump 23 are formedin the opening parts formed by removing the resist 34. The bumps 13 areformed at the positions at which the base electrodes 12 are disposed.The bump 23 is formed at the position at which the base electrode 22 isdisposed. In the present embodiment, the bumps 13 and the bump 23 areformed through electroless plating as an example. In the electrolessplating, plating forming the bumps 13 and the bump 23 is attached to thesurfaces of the base electrodes 12 and the base electrode 22. As theplating grows, the bumps 13 and the bump 23 are formed. The bumps 13 andthe bump 23 are simultaneously formed. The height of the bumps 13 fromthe surface of the semiconductor substrate 2 and the height of the bump23 from the surface of the semiconductor substrate 2 are substantiallythe same. Since the bumps grow isotropically with respect to the baseelectrodes in the electroless plating, the bump 23 can be formed furtheroutside than the range in which the base electrode 22 is disposed.Although the method of forming the bumps through electroless plating hasbeen described in the present embodiment, the bumps may be formed usinga method other than electroless plating.

FIG. 2D shows a state in which, after the bumps 13 and the bump 23 areformed, the resist 34 is removed. The bumps 13 are formed so that partsof the surfaces of the base electrodes 12 are exposed. The bump 23 isformed to cover the entire surface of the base electrode 22.

In the present embodiment, alignment can be performed such that apositional deviation of the bumps 13 occurring during formation of thebumps 13 is absorbed.

FIG. 3 shows a cross-section of the semiconductor device according tothe present embodiment in the alignment process of the semiconductordevice. In the semiconductor device 3 shown in FIG. 3, there is apositional deviation of the bump 13 occurring when the bump 13 is formedon the surface of the base electrode 12. When the bump 13 deviates fromthe base electrode 12 in the process of forming the bump 13 and the bump23, the bump 23 likewise deviates from the base electrode 22. The amountof the positional deviation of the bump 23 is substantially the same asthe amount of the positional deviation of the bump 13. For this reason,even when the bump 13 deviates from the base electrode 12 and the bump23 deviates from the base electrode 22, the distance between the bump 13and the bump 23 is substantially the same as the designed value.

In the alignment process of the semiconductor device according to thepresent embodiment, alignment is performed with reference to thedistance between the base electrode 21 and the bump 23. For this reason,when alignment is performed so that the distance between the baseelectrode 21 and the bump 23 is uniform within the alignment mark 20,the positions of the base electrode 11 and the bump 13 are aligned witheach other. In other words, even though the bump 13 deviates from thebase electrode 12, alignment can be performed with high accuracy so thatthe position of the base electrode 11 is aligned with the position ofthe bump 13 (see the region surrounded by the dashed line A of FIG. 3).Therefore, in the semiconductor device according to the presentembodiment, connection strength of the connection part, an electricalcharacteristic of the connection part, and the like can be improved.

FIG. 4 shows a state in which the semiconductor substrate 1 and thesemiconductor substrate 2 constituting the semiconductor device 3according to the present embodiment are seen in plan view. A pluralityof chips are disposed in the respective semiconductor substrate 1 andthe semiconductor substrate 2. A plurality of chips C1 are disposed onthe semiconductor substrate 1. A plurality of chips C2 are disposed onthe semiconductor substrate 2. After the semiconductor substrate 1 andthe semiconductor substrate 2 are connected to each other, the connectedsubstrates are divided into the plurality of chips. The chip C1 and thechip C2 after the division constitute one semiconductor device.

In FIG. 4, positions of the internal constitutions of the chips when thechip C1 and the chip C2 are seen in plan view are shown. In the exampleshown in FIG. 4, a semiconductor device constituted by the chip C1 andthe chip C2 is a solid-state imaging device 4.

The chip C1 has a pixel circuit region (photoelectric conversionelement) 40. The pixel circuit region 40 is a region in which aplurality of pixels which include the photoelectric conversion elementwhich outputs signals depending on an input light amount aretwo-dimensionally arrayed. At an end part of the chip C1, the baseelectrode 21 constituting the alignment mark 20 is disposed.

The chip C2 has a signal-processing circuit region (processing circuit)50, a vertical scanning circuit region 51, and a horizontal scanningcircuit region 52. A readout circuit and a processing circuit aredisposed in the signal-processing circuit region 50. The readout circuitincludes a capacitor which accumulates signals generated by thephotoelectric conversion element of the pixel circuit region 40 and aMOS transistor which reads out the signals accumulated in the capacitor.The processing circuit performs an analog signal process such asamplification and noise removal on a read out signal. A verticalscanning circuit which outputs control signals for performing processeson each row of the pixel array is disposed in the vertical scanningcircuit region 51. A horizontal scanning circuit which outputs controlsignals for sequentially outputting signals processed in thesignal-processing circuit region 50 to the outside is disposed in thehorizontal scanning circuit region 52. The base electrode 22 and thebump 23 constituting the alignment mark 20 are disposed at an end partof the chip C2. The base electrode 22 is not illustrated in FIG. 4.

FIG. 5 shows a configuration of an imaging device which has asolid-state imaging device that is an example of the semiconductordevice according to the present embodiment. The imaging device accordingto an aspect of the present invention may be an electronic apparatuswith an imaging function, or may be a digital camera, a digital videocamera, an endoscope, or the like.

The imaging device 200 shown in FIG. 5 includes a lens 201, an imagingunit (solid-state imaging device) 202, an image-processing unit 203, adisplay unit 204, a drive control unit 205, a lens control unit 206, acamera control unit 207, and a camera manipulation unit 208. FIG. 5 alsoshows a memory card 209. The memory card 209, however, may be configuredto be attachable to and detachable from the imaging device, andtherefore the memory card 209 need not be an intrinsic constitution ofthe imaging device.

The lens 201 is a photographing lens for forming optical images ofsubjects on an imaging plane of the imaging unit 202 which constitutesthe solid-state imaging device. The imaging unit 202 converts an opticalimage of a subject formed by the lens 201 into a digital image signalthrough photoelectric conversion, and outputs the image signal to theimage-processing unit 203. The image-processing unit 203 performsvarious digital image processes on the image signal output from theimaging unit 202.

The display unit 204 displays images based on images signals which haveundergone image processes for display by the image-processing unit 203.The display unit 204 can not only display still images but can alsoperform dynamic image (live view) display in which images of a capturingrange are displayed in real time. The drive control unit 205 controlsoperations of the imaging unit 202 based on instructions from the cameracontrol unit 207. The lens control unit 206 controls the stop and focuspositions of the lens 201 based on instructions from the camera controlunit 207.

The camera control unit 207 controls the entire imaging device 200.Operations of the camera control unit 207 are regulated by a programstored in a ROM included in the imaging device 200. The camera controlunit 207 reads out this program and performs various controls inaccordance with the content regulated by the program. The cameramanipulation unit 208 has various members for manipulations for a userperforming various manipulation inputs with respect to the imagingdevice 200. The camera manipulation unit 208 outputs signals based onresults of the manipulation inputs to the camera control unit 207. As aspecific example of the camera manipulation unit 208, a power switch forturning on and off the power of the imaging device 200, a release buttonfor instructing photographing of a still image, a still-imagephotographing mode switch for switching a still-image photographing modeinto a single-shoot mode and a continuous-shoot mode, and the like areexemplified. The memory card 209 is a recording medium for saving imagesignals processed by the image-processing unit 203 for the purpose ofrecording.

Next, a modified example of the semiconductor device according to thepresent embodiment will be described. FIGS. 6 and 7 show other examplesof the shape of the alignment mark. The upper drawings of FIGS. 6 and 7show states in which alignment marks provided on the semiconductordevice are seen in plan view. The lower drawings of FIGS. 6 and 7 show across-section of the semiconductor device.

In the semiconductor device shown in FIG. 6, the shape of the alignmentmark 20 is a quadrangle shape. To be more specific, when thesemiconductor substrate 1 and the semiconductor substrate 2 are seen inplan view, the base electrode 21 has a quadrangle (square) shape whoseinner part is hollow, and the base electrode 22 and the bump 23 havequadrangle (square) shapes. As described, a shape of the alignment mark20 may be a polygonal shape having three or more angles. An angle of thepolygonal shape of the alignment mark 20 may be rounded. In the presentembodiment, the base electrode 21 constituting the alignment mark 20 isformed to surround the perimeter of the bump 23. The base electrode 21,however, may not surround the perimeter of the bump 23.

In the semiconductor device shown in FIG. 7, the shape of the alignmentmark 20 is a more complicated shape. To be more specific, when thesemiconductor substrate 1 and the semiconductor substrate 2 are seen inplan view, the base electrode 22 has a cross shape, and the baseelectrode 21 is divided into four quadrangles. The four pieces of thebase electrode 21 are respectively disposed in four spots of theupper-left, upper-right, lower-left, and lower-right sides of the baseelectrode 22. In an alignment process using the alignment mark 20 shownin FIG. 7, relative positions of the semiconductor substrate 1 and thesemiconductor substrate 2 in the horizontal direction are adjusted sothat respective distances between the four pieces of the base electrode21 and the bump 23 are all a distance L. In comparison to the alignmentprocess using the alignment mark 20 shown in FIG. 1, the number of spotson which gaps of the alignment mark are to be checked further increasesin the alignment process using the alignment mark 20 shown in FIG. 7.For this reason, accuracy in alignment is further improved.

A shape of an alignment mark may be one other than the shape of thealignment marks shown in FIGS. 1, 6, and 7. An alignment mark may beconfigured to include at least a first mark that is disposed on a firstsubstrate and a second mark that is disposed at a position on a secondsubstrate which corresponds to the position of the first mark. A shapeof an alignment mark may be one which enables alignment.

The bump 23 is formed on the semiconductor substrate 2 in thesemiconductor device 3 shown in FIG. 1. The bump 23, however, may beformed on the semiconductor substrate 1. FIG. 8 shows anotherconfiguration of the main part of the semiconductor device 3 which hasthe semiconductor substrate 1 on which the bump 23 is formed. The upperdrawing of FIG. 8 shows a state in which the alignment mark provided inthe semiconductor device 3 is seen in plan view. The lower drawing ofFIG. 8 shows a cross-section of the semiconductor device 3. Differencesfrom the configuration shown in FIG. 1 will be described below.

The ring-shaped base electrode 21 is formed on a surface of thesemiconductor substrate 2, and the circular-shaped base electrode 22 andbump 23 are formed on a surface of the semiconductor substrate 1. Thebase electrode 22 is connected with a through-hole 35 that is formedinside the semiconductor substrate 1. The through-hole 35 is exposed onthe surface of the semiconductor substrate 1. The exposed portion of thethrough-hole 35 is connected with the base electrode 22. Thethrough-hole 35 is connected to a wiring layer formed inside thesemiconductor substrate 1, which is not illustrated.

In the semiconductor device 3 shown in FIG. 8, the semiconductorsubstrate 2 corresponds to a first substrate. The semiconductorsubstrate 1 corresponds to a second substrate. The base electrode 12corresponds to a first electrode disposed on the first substrate. Thebase electrode 11 corresponds to a second electrode disposed on thesecond substrate. The base electrode 21 corresponds to a first markdisposed on the first substrate. The bump 23 corresponds to a secondmark disposed at a position on the semiconductor substrate 2 whichcorresponds to the position of the first mark.

When the semiconductor device is a solid-state imaging device, the pixelcircuit region 40 is disposed on the semiconductor substrate 1, and thesignal-processing circuit region 50, the vertical scanning circuitregion 51, and the horizontal scanning circuit region 52 are disposed onthe semiconductor substrate 2 as shown in FIG. 4. In the semiconductordevice 3 shown in FIG. 8, the bump 23 is formed on the surface of thesemiconductor substrate 1 on which the pixel circuit region 40 whichincludes a photoelectric conversion element is disposed. A manufacturingprocess of the connection part 10 and the alignment mark 20 is the sameas that shown in FIGS. 2A to 2D.

As described above, according to the semiconductor device 3 according tothe present embodiment, the sum of the height of the base electrode 21and the height of the bump 23 is substantially equal to the sum of theheight of the base electrode 11, the height of the base electrode 12,and the height of the bump 13. For this reason, the position of thesurface of the base electrode 21 and the position of the surface of thebump 23 are substantially the same in the direction perpendicular to themain surface of the semiconductor substrate 1 or the semiconductorsubstrate 2. Accordingly, the positions can be focused, and thereforeaccuracy in alignment can be improved.

Since the base electrode 21 and the bump 23 constitute the alignmentmark, an alignment mark can be formed using a manufacturing process offorming the base electrode 11 and the bump 13.

When the semiconductor substrate 1 and the semiconductor substrate 2 areseen in plan view, the base electrode 21 and the bump 23 are formed suchthat the base electrode 21 surrounds the perimeter of the bump 23. Forthis reason, alignment can be easily performed with reference to thedistance between the inner circumference of the base electrode 21 andthe outer circumference of the bump 23.

The base electrode 22 and the bump 23 are formed such that the bump 23is disposed on the surface of the base electrode 22 and the width of thebase electrode 22 is equal to or smaller than the width of the bump 23.For this reason, alignment can be performed in the state in which theouter circumference of the bump 23 is not obstructed by the baseelectrode 22. Thus, accuracy in alignment can be improved.

Although the configuration of the semiconductor device in which the twosubstrates are connected by the connection part has been shown in thepresent embodiment, three or more substrates may be connected by aconnection part. In the case of a semiconductor device in which three ormore substrates are connected by a connection part, two out of the threeor more substrates correspond to a first substrate and a secondsubstrate.

Although exemplary embodiments of the present invention have beendescribed above, the present invention is not limited thereto. Addition,omission, substitution, and other modifications may be made to thepresent invention without departing from the spirit and scope of thepresent invention. The present invention is not limited by the abovedescription, but only limited by the accompanying claims.

What is claimed is:
 1. A semiconductor device comprising: a firstsubstrate; a second substrate; a connection part which electricallyconnects the first substrate and the second substrate; and an alignmentmark which is used in alignment of the first substrate and the secondsubstrate, wherein the connection part includes: a first electrode whichis disposed on the first substrate; a second electrode which is disposedon the second substrate; and a connection bump which is disposed betweenthe first electrode and the second electrode and which electricallyconnects the first electrode and the second electrode, wherein thealignment mark includes: a first mark which is disposed on the firstsubstrate; and a second mark which is disposed on the second substratesuch that the second mark is aligned with respect to the first markwithin a predetermined alignment error, the second mark being insulatedfrom the first mark, and wherein a sum of a height of the first mark anda height of the second mark is substantially equal to a sum of a heightof the first electrode, a height of the second electrode, and a heightof the connection bump.
 2. The semiconductor device according to claim1, wherein the height of the second mark is substantially equal to a sumof the height of the second electrode and the height of the connectionbump.
 3. The semiconductor device according to claim 2, wherein thefirst mark is an electrode which is disposed on the first substrate, andwherein the second mark is a bump which is disposed on the secondsubstrate.
 4. The semiconductor device according to claim 3, wherein,when the first substrate and the second substrate are seen in plan view,the first mark surrounds the second mark.
 5. The semiconductor deviceaccording to claim 3, wherein the bump is connected with the secondsubstrate and a surface of a base electrode which is formed on a surfaceof the second substrate, and wherein a width of the base electrode isequal to or smaller than a width of the bump.
 6. A solid-state imagingdevice comprising: the semiconductor device according to claim 3,wherein the second substrate includes a photoelectric conversion elementwhich is configured to output a signal depending on an amount ofincident light, and wherein the first substrate includes a processingcircuit which is configured to process the signal output from thephotoelectric conversion element.
 7. An imaging device comprising: thesolid-state imaging device according to claim
 6. 8. A solid-stateimaging device comprising: the semiiconductor device according to claim1, wherein the first substrate includes a photoelectric conversionelement which is configured to output a signal depending on an amount ofincident light, and wherein the second substrate includes a processingcircuit which is configured to process the signal output from thephotoelectric conversion element.
 9. An imaging device comprising: thesolid-state imaging device according to claim 8.